For 2010, the Chevrolet Silverado and GMC Sierra are more fuel efficient thanks to some subtle changes from GM engineers. Regular trucks with the 5.3-liter V-8 climb from 14 mpg city/20 mpg highway to 15/21; the fuel-sipping XFE models earn 1 extra highway mpg, for a rating of 15/22. Figures for hybrid variants of the Silverado and Sierra are unchanged.

The changes needed for these improvements reportedly don’t affect the payload, horsepower, or tow ratings of the trucks. New shift points for the trucks’ six-speed automatic and a lower 3.08 final drive ratio, as well as variable valve timing and Active Fuel Management (which sometimes runs the V-8 on only four cylinders to save fuel) help achieve the higher numbers.

If 1 mpg doesn’t seem like a big difference, consider this: improving from 14 mpg to 15 saves about the same amount of fuel as a car that gets 40 mpg instead of 33.